The present invention relates to communications systems, and more particularly to location area registration in communications systems.
Wireless communications networks of today continually track mobile terminal movement within an overall network coverage area so that incoming traffic can be routed to intended mobile terminal destinations quickly and efficiently. Such tracking is typically accomplished by way of mobile terminal location updates or registrations. In other words, each mobile terminal within a network coverage area typically notifies the network whenever the mobile terminal changes location.
In order to reduce the frequency of location updates and to thereby reduce the associated processing overhead, the overall coverage area of a network is typically divided into multiple location areas within which mobile terminals can move around without having to notify the network. In practice, the size of each location area represents a trade off between the traffic load caused by location updates and that caused by the paging required to notify mobile terminals of incoming traffic. Generally, the larger a location area is, the fewer location updates are required to track mobile terminal movement and the more base stations are involved in paging.
Today, most cellular systems use a single set of static location areas for every terminal within a network. The more advanced schemes (e.g., Personal Digital Cellular or PDC) use overlapping location areas and track hysteresis at the area borders to provide different terminals with different effective location areas. The overlapping location areas are nonetheless of fixed shape and size. Since the optimal shape and size of a location area is ultimately dependent upon terminal type and terminal user behavior, as well as the particular application a terminal user is running, location areas are ideally customized specifically for each user and/or for each terminal. Several schemes for customizing location areas for specific terminals are being developed at the research level.
No matter which particular type of location area scheme is preferred, however, conventional techniques permit only one type of location area scheme to be employed within a given system or network. In other words, to achieve compatibility across a given system or network, all equipment within the system or network is constructed consistently to utilize a single, common location area registration scheme. Equipment utilizing different types of location area registration cannot coexist, and varying levels of location area registration complexity cannot be achieved.
As a result, today's networks are difficult to upgrade. In other words, since all equipment within a network must utilize a common location area registration scheme, all network equipment must be upgraded simultaneously. Also, because such network-wide upgrades can be prohibitively costly and protracted, it is often difficult to introduce a more advanced location area registration scheme or to standardize an improved location area algorithm. For example, since tremendous effort must be put forth to implement even the first version of a new standard, the proposed customized-location area schemes described above have been less attractive than they would otherwise be to standardization bodies. As a result, the significant advantages provided by such schemes are presently being under utilized.
Furthermore, known techniques for implementing location area registration schemes are not suitable for the flexible and powerful "universal" networks being proposed today. For example, PCT Publication No. 96/34504, published Oct. 31, 1996 and entitled "Method and Arrangement for Increasing the Range for a Telecommunication Network in a Telecommunications System" (and corresponding to PCT Application No. PCT/SE96/00510 filed Apr. 18, 1996), describes a Generic Radio Access Network (GRAN) which is now being targeted for standardization by the European Telecommunications Standards Institute (ETSI) in the Universal Mobile Telecommunications System (UMTS) standardization work.
The Generic Radio Access Network, now also known in the art as the UMTS Radio Access Network (URAN), provides a generic interface to which any type of service network can connect. Future service networks can be tailored to explicitly fit the generic interface, and existing service networks (e.g., the Global System for Mobile Communications (GSM), the Integrated Services Digital Network (ISDN), the Public Switched Telephony Network (PSTN), etc.) can utilize an appropriate intermediary or interworking function (IWF). Terminals used to access the Generic Access Radio Network are divided logically into two parts, one part logically belonging to the Generic Radio Access Network itself and another part logically belonging to a particular service network to which the terminal user subscribes.
The Generic Radio Access Network itself has no direct subscribers. Rather, terminal users subscribe to services within their respective service networks, and the service networks in turn connect with generic bearer services offered by the Generic Radio Access Network. The service networks then use the bearer services to connect with their subscribers and thereby extend the range of their networks and provide increased mobility to their subscribers.
To provide these advantages, the bearer services offered by the Generic Radio Access Network are extremely flexible and are capable of providing diverse signaling and traffic connections that match those of the many existing and yet to be developed service networks which will ultimately utilize the Generic Radio Access Network. By way of contrast, the above described conventional techniques for implementing location area registration schemes are inflexible and therefore inadequate in the context of universal networks such as the Generic Radio Access Network. In other words, since universal networks are designed to allow differently configured equipment to coexist, conventional techniques requiring that all equipment be uniformly configured to utilize a common registration scheme are inapplicable.
Thus, there is a need for improved methods and apparatus for implementing location area registration schemes in communications systems.